The prevalence of dementia, its public health importance, and its effect on health care costs have now been documented in a variety of populations. Further elucidation of the incidence, risk factors, associated features, and distribution of the different dementing disorders requires longitudinal studies of well-characterized population samples. A major obstacle to conducting such studies is the absence of normative population data on cognitive functioning and change over time. The current proposal seeks to continue an ongoing prospective community study of cognitive impairment and dementia in the rural mid-Monongahela Valley region of Southwestern Pennsylvania, about 25 miles south of Pittsburgh. A cohort of non-institutionalized persons aged 65 and older, who met basic education and fluency criteria, was assembled as part of a survey to establish a population-based dementia registry starting in 1987. This cohort was made up of an age-stratified random sample of 1366 and a volunteer sample of 259 subjects. Since 1989, the survivors of the cohort have been followed with repeated cognitive screening at 18-24 month intervals, with the primary goals of identifying incident cases of dementia and risk factors for dementia, as well as normal and abnormal patterns of cognitive change over time. We propose to follow the cohort with identical methods over a further 5-year period, so as to accrue a greater number of incident cases and maximize the utility of existing baseline and followup data enabling us to identify predictors of cognitive decline and dementia. We will also accumulate a larger number of outcome events (institutionalization and death) so as to identify the predictors of these outcomes. Progress to date is reported, including data on comorbidity of dementia and on cognitive decline in the cohort over the first followup period. Additional objectives are to refine cognitive screening methodology, particularly for distinguishing normal from abnormal decline, and to explore the pharmacoepidemiology of cognitive impairment and dementia.